The importance of tight glycemic control to prevent complications has been well documented. More recently, studies indicate that postprandial glucose is an independent risk factor for the development of macrovascular complications (1-3). Many well controlled patients with diabetes have significant postprandial hyperglycemia. Therefore, an alternative marker that more robustly reflects postprandial glucose excursions than A1C measurements could be beneficial in the long-term care of patients with diabetes. Here, “glucose excursion” means a movement in the amount of glucose in blood from one level to another, usually with the implication that the amount will eventually return to the original level, and “A1C” or equivalently “HbA1c” refers to glycosylated hemoglobin.
1,5-Anhydro-D-glucitol (hereafter abbreviated to 1,5-anhydroglucitol or “1,5-AG”) is a naturally occurring dietary polyol having a very similar chemical structure to glucose and present in human cerebrospinal fluid and plasma. Its quantity in plasma is stable in healthy subjects and is reduced in those with certain diseases, particularly with diabetes.
Plasma levels of 1,5-AG fall as urinary glucose appears, generally at around 180 mg/dL, which is the renal threshold for glucose and the upper limit of normal postprandial glucose. Thus, the 1,5-AG test responds sensitively and rapidly to serum glucose levels, reflecting even transiently ascending serum glucose above the renal threshold for glucosuria within a few days (4,5). In contrast, A1C is a reflection of average glucoses over a much longer period of time (2-3 months), encompassing both hyperglycemic and hypoglycemic periods. Therefore, glycemic excursions are “averaged out” in the setting of A1C monitoring.
In clinical setting, 1,5-AG in plasma or serum can be measured conveniently by a commercial kit based on colorimetric enzymatic method using an enzyme that oxidizes 1,5-AG.